Age of Appearance of IgG, IgM, and IgE Antibodies Specific for Loa loa in Gabonese Children

Abstract

IgG, IgM, and IgE antibodies against the filaria Loa loa were measured in umbilical cord blood and in blood from young Gabonese children by an ELISA technique using a homologous metabolic antigen. For children in eight consecutive age groups and adults the percentage of the population positive for each of the antibody classes was determined. The number of children with maternal IgG decreased until one year of age when new synthesis began to become apparent. 1gM antibodies were detected only after six months, probably indicating an early infancy as opposed to a fetal infection. The percentage of individuals positive for IgM or IgEE reached a peak between two and three years old, followed by a slight decline. Over half of the individuals over one year of age had IgM antibody against L. loa, indicating long-term synthesis of this class of immunoglobulin in many people. In the first two years of life, IgE antibodies were usually accompanied by L. loa-specific IgM. This specific IgE did not appear to trigger the synthesis of nonspecific IgE. By the age of two, 95°-(, of the population had some antibodies against L. loa and by five the percentage of individuals positive for each antibody class had reached adult levels.Infestation with the filaria Loa loa is very common in certain parts of equatorial Africa and is highly endemic in Gabon (2,3,7,8). The diagnosis of Loa loa infec tionby microscopic identification of microfilariae in the blood does not reveal all infections, particularly in children where microfilariae are rarely seen (2).The development of an ELISA method for the determination of L. loa-specific antibodies that do not appear to cross-react with Dipetalonema perstans (4) has per mittedus to titrate not only IgG and IgM, but also IgE. This latter class of im munoglobulinis important in immediate hypersensitivity and in host-parasite interactions (6), but because of its low concentration in the blood, it is difficult to measure.In addition, total IgE has been measured as, according to Ishizaka et al (5), specific IgE synthesis primes the production of nonspecific IgE.In this investigation, we have studied the immunological status of Gabonese children in regard to L. loa in order to identify the age at which antibodies are first observed and the age at which the percentage of individuals positive for each class of immunoglobulin is the same as in adults. 787

Humoral responses to a secretory Onchocerca volvulus protein: differences in the pattern of antibody isotypes to recombinant Ov20/OvS1 in generalized and hyperreactive onchocerciasis

“…This finding is in accordance with the larger numbers of IgG4‐producing plasma cells in the nodules from patients with generalized onchocerciasis compared to those with the hyperreactive form (Büttner, unpublished data). A continuous synthesis of IgM, an antibody predominating in the early humoral responses to parasite infections, has been reported in Loa loa infection ( Goussard et al . 1984 ).…”

Antibody‐dependent cell‐mediated immune reactions to Loa loa microfilariae in amicrofilaraemic subjects

“…It was estimated recently that individuals receive 20-24 infective fly bites per year (Noireau et al 1990). In addition, seropositivity is very high, in one hyperendemic zone 95% of the inhabitants had antibodies reacting with L. loa antigens by the age of two years (Goussard et al 1984). Yet, despite heavy exposure to infection the prevalence of microfilaraemia rarely exceeds 30% (Fain et al 1974, Van Hoegaerden et al 1987 and after the age of 20 years the intensity of infection does not increase with age (Kershaw & Nicholas 1954, Noireau et al 1989).…”

The Population Biology and Transmission Dynamics of Loa loa

“…The second is that a high proportion of parasitised subjects (as determined by signs of apparent infection such as history of eyeworm), do not present with microfilaraemia (although a similar phenomenon is also observed in LF [72]). Indeed, despite high prevalence of apparent infection (history of eyeworm), which in hyperendemic regions can surpass 70% [4], with 95% of the population possessing antibodies reacting with L. loa antigens by the age of 2 years [73], the proportion of people with microfilaraemia (assessed by microscopy) is often far lower, typically representing 30-40% of the total population, and only 50-60% in highly endemic areas (and even then only in adults older than 50 years of age) [70]. It is often, therefore, concluded that a substantial fraction of the population is amicrofilaraemic [74].…”